Sodium Fluoride
by JoeMerl
Summary: Seamus Finnigan has one tube of toothpaste, three semi-helpful friends and less than thirty minutes to complete his Muggle Studies assignment. He also has a distinct capacity for causing explosions. One-shot, done for the N.E.W.T.s Challenge.


**Author's Notes:** This was done for the N.E.W.T.s Challenge, wherein I chose a class (Muggle Studies) and was assigned a character (Seamus Finnigan) and prompt (toothpaste). I'm not used to writing him or Dean, so I hope this came out alright.

* * *

It was the first Thursday of term and Seamus Finnigan was kneeling in front of his trunk, growing increasingly frantic as he threw his possessions onto the floor and bed.

"Uh...looking for something?"

Seamus jumped, then spun around to find his best friend in the threshold of the dormitory. "Dean!" he said, crossing the room in half a second and grabbing his startled friend by the shoulders. "You've gotta help me! I need something—_Muggle_ right now!"

"Huh?!"

"For my Muggle Studies class!" Seamus released Dean and ran his hands through his hair, a nervous habit of his. "It was our homework assignment over the summer—get some sort of Muggle thing and then write up a presentation to give in front of the class. I was supposed to pack my dad's electric drill, but it's not in my trunk! I must have left it at home or something!"

"So? Write to your parents. They could send an owl by tomorrow."

"The assignment is due in _less than half an hour!_"

"What?! You had all summer and you waited until the last thirty minutes to even _start?!_ Wait, I know you, why am I even surprised?"

"_Just help me!_ Lend me something—Muggley. Like..."

His eyes wandered over to unmoving West Ham football poster hanging above Dean's bed. "Oh, no-no-no!" Dean said, moving in front of it and holding his arms out at his sides. "No way!"

"Come on! I only need it for an hour!"

"I don't care! This poster is of the team back in 1969! It was my dad's most prized possession before he gave it to me. I'm not gonna let you destroy it."

"I'll be careful with it!"

"Seamus, the other day you accidentally set my hair on fire. _In History of Magic._"

"Well, give me something else, then!"

Dean sighed, then bent down to open his trunk. "Alright—but I'm honestly not sure if I have anything," he said, taking out some robes and piling them on his bed. "There's no point taking any Muggle stuff here, half of it I don't need and the other half doesn't even work...how about some Muggle clothes?"

He held up a shirt and a pair of jeans. Seamus scowled. "Dean, _everyone_ has at least one pair of trousers—half the Pureblood kids are going to bring stuff like _that_ just because they're lazy."

"As opposed to you, the pinnacle of productivity."

"Isn't there anything else?!"

"Not really. Uh, I have a piece of parchment where I wrote down some football scores? And, uh..._"__  
_

"What happened here?"

Dean and Seamus turned as Harry and Ron came into the dormitory. Once again Seamus was across the room, this time gripping Harry by the arm.

"Harry! You're Muggle-born! Or—Muggle-raised, anyway. _You_ have to have something that I can use for my Muggle Studies assignment, right?"

"Er—what do you need?"

"_Anything!_"

"Well, unless that includes one of my uncle's old socks, I'm not sure I can help. My Muggle relatives aren't exactly the most generous bunch."

Seamus let out a groan of frustration. Dean continued to dig through his trunk, and Ron bent down to help him.

"Um...Dean? Is this bra yours?"

"What?! Oh, _ugh,_ some of my sister's laundry must have gotten mixed in with mine." He snatched the offending garment from Ron and threw it back down to the bottom of his trunk. "Uh...how about this, Seamus?"

Seamus turned, then took the item from Dean, frowning. "_Toothpaste?_"

"Muggle toothpaste," Dean said, a bit defensively.

"_Wizards have toothpaste too!_"

"But it'll be a different kind of toothpaste," Ron noted. "It'll be made with—you know, those things Muggles use instead of potions?"

"Chemicals," Harry supplied.

"Yeah."

Seamus sighed. "It's the best I've got, I guess."

He grabbed up a quill, parchment and ink bottle from the mess on the floor, closing his trunk to use as an awkward writing desk. He examined the toothpaste with a frown. "Okay—uh, the tube says it has '_multi-benefits...'_" He began to scribble. "_'Cleans...freshens...protects against gum disease...'_"

"The magic toothpaste we have here says basically the same thing."

"Mention the chemicals," Ron advised.

"_'Made of chemicals'..._is that spelled with a 'k' or a 'c?'"

"Yeah, something tells me you're not going to do all that well on this assignment, mate."

"Shut up, Harry. Okay—what kind of chemicals are in these?" He turned the tube around. "_'Active ingredients: Sodium fluoride.__' _What does that do?"

He looked expectantly at Dean and Harry. They looked at each other.

"Uh...no idea."

"_No idea?!_ Are you Muggle-borns or not?!"

"_Not,_" Harry said.

"And being at Hogwarts? That sort of means we haven't taken any secondary school chemistry classes," Dean groused.

"Well, what am I supposed to write, then?!"

"Wait—the Muggle Studies teacher hasn't taken these—chemical-sty classes either, right?" Ron asked, looking at the others in turn. "She won't be able to tell if you just make something up. Just say it cleans your mouth or kills germs or something."

"That's a good idea. _'Sodium fluoride kills mouth germs...'_"

"Remember, that's 'germs' with a 'g,' not a 'j.'"

"I know that!" Seamus snapped, nonchalantly crossing out _jurms_ on his parchment. "What time is it?"

"Given how far Professor Burbage's class is from here? About five minutes before you have to leave."

"Well, what else can I say, then?!"

"Er—taste?" Harry suggested.

"Taste? Hmm." Seamus undid the cap and squeezed a half-inch of toothpaste onto his tongue; Ron and Harry grimaced as his face puckered thoughtfully. "Minty. Maybe a little stronger than the toothpaste we have here." He scribbled that down.

"It also doesn't make your gums itch for half an hour after you use it, like the toothpaste we get here," Dean said.

Harry frowned. "It's never done that for me."

"Me neither."

"Really? I can barely stand using it. That's why I always get toothpaste from home instead."

Ron snapped his fingers. "You know what it might be? Maybe you're allergic to one of the potions in it. Like with my brother Charlie—it used to be that every time he got a cold, he also broke out in these really bad boils. Eventually my mum figured out that it was actually the Pepperup Potion she used that—"

"Hey, mates? This is all fascinating, but it's _not helping me at all!_"

"Well, put down the thing about the itching! Say that the Muggle toothpaste, I don't know, provides a valuable option for people with allergies."

"That's stupid," Seamus muttered as he wrote it down. He stopped and surveyed his work. "Well, it's not quite ready for my O.W.L.s, but I should be able to stretch this out into a two-minute presentation. Now where's my bag?"

Harry found it among the mess on the floor; Seamus quickly threw in the toothpaste and parchment. "I have to go. Thanks for all your help, mates!"

He dashed out of the dormitory. Dean, Harry and Ron glanced at each other, then at the mess on the floor.

"He better not expect one of us to clean this all up."

* * *

The entrance the Gryffindor Tower was on the seventh floor; the Muggle Studies classroom was on the first. Seamus checked his watch—if he took a few secret passageways he might not be late, but he was really going to have to run.

But unbeknownst to him, every step he ran jostled the wand inside his bag, making it jab against the toothpaste container. And every time it jabbed a few sparks flew out, and the tube began to grow fatter...

* * *

Gryffindors had a double Muggle Studies lesson with the Hufflepuffs, which meant that going alphabetically, Seamus' presentation would come right after Justin Finch-Fletchley's.

Seamus sort of hated having Muggle Studies with Justin Finch-Fletchley. He was a Muggle-born and kind of a swot; Seamus was pretty sure that he only took this class to make people from Wizarding families look bad.

"...allowing the cell phone to work without the use of cords," he concluded, after a six-minute presentation that included a long tangent about space.

Professor Burbage clapped excitedly, and about half of the class (mostly Hufflepuffs) joined her. "Very good, Justin, very good!" she said as he sat down and beamed. "And everyone, I know O.W.L.s are a ways off, but a little motivation—we'll be learning more about satellites in our N.E.W.T. class! Alright, next is...Seamus! Let's see what he has to show us today."

Seamus took a deep breath as he rose to his feet, pulling his bag off the floor and onto his desk. "Well," he said, looking a bit peaky as he dug through its clutter, "I brought something that—er—is a common item for both Muggles and wizards, but which is...very..._huh?_"

He stared at the tube of toothpaste, sitting in the bag beside his wand, swollen like a massive sausage and trembling by its own power. He pulled it out and held it in the palm of his hand, raising an eyebrow. His touch seemed to aggravate it, though, as it began to rock from side to side, faster and faster—

_PLUUURRRTTT!_

"_EWW!_"

The tube suddenly exploded, and several of Seamus' neighbors jumped back in an unsuccessful attempt to avoid being splattered with toothpaste; Seamus, of course, received the brunt of it and screamed, dropping the ruptured plastic as the sticky blue gel sting in his eyes. A few people laughed as Seamus groaned in disgust, his hand and face covered with toothpaste, trying to wipe both of his robe. He sputtered and spat, the taste of mint overpowering him.

"Oh, dear!" Professor Burbage said, looking Seamus up and down. "Are you alright?"

Seamus opened his eyes, which were still watering, and reached into his bag again. He took out his wand, which was sparking slightly, and threw it back down in disgust.

"So. Muggle toothpaste," he said through gritted teeth. "It contains—soodium Floo Powder, or something, which—_apparently_ has explosive qualities when in contact with laurel wood and dragon heartstring."

A few people snickered. Professor Burbage looked pained as she cast a Scouring Charm on Seamus and his neighbors, eliminating the toothpaste but leaving a light sprinkling of soap suds. "I...think that will be enough, Seamus. Please take your seat."_  
_

He sat down and grumbled as Professor Burbage called on Wayne Hopkins, who took out a ball and began explaining rugby to the class.


End file.
